Microstructure and Electrochemical Properties of ZnMn2O4 Nanopowder Synthesized Using Different Surfactants

ZnMn2O4 (ZMO) nanopowders have been synthesized by a hydrothermal method using different surfactants [cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG)-400, and Polysorbate-80]. The as-prepared ZnMn2O4 samples exhibited single phase with tetragonal structure, showing honeycomb, spinel microsphere, and flower-cluster morphology, respectively. Cyclic voltammetry curves for all samples presented rectangular shape with symmetric nature and good cycling properties, with no obvious redox peak. Galvanostatic charge-discharge curves were triangular and symmetric. The specific capacitance of the ZnMn2O4 nanopowders gradually decreased with increase of the scanning rate. ZMO-PEG exhibited higher specific capacitance of 191Fg(-1) at scan rate of 5 mVs(-1) and retained superior large-current cycling stability of 98.4% after 1000 cycles compared with ZMO-CTAB (93.8%) or ZMO-Polysorbate-80 (97.7%). Electrochemical impedance spectroscopy revealed that the ZnMn2O4 nanopowders had low resistance. These results suggest that ZnMn2O4 nanopowders have good capacitance characteristics.